ONE OF THE MORE unpleasant reactions to the terrorist attacks of 9/11 was the nearly spontaneous birth of a community of skeptics questioning the "official" storyline of events. Somehow these theories seem to have gathered steam in recent years.

The conspiracy theories are legion: the twin towers were brought down by a controlled demolition and not airplanes; the towers were brought down by airplanes, but the airplanes were laden with explosives; the Pentagon was struck not by a passenger jet, but by a missile; United Flight 93 did not crash, but was shot down by an F-16. All of these theories incorporate tiny pieces of "evidence" (or the absence of evidence) and lead to the same conclusion: that a massive conspiracy was orchestrated by a shadowy faction of the United States government in order to draw the country into a global conflict with Islam.

While composing their report, the 9/11 Commission was faced with the difficult decision of how to deal with these rumors. "We discussed the theories," the commission's executive director, Philip Zelikow, told the Washington Post. "When we wrote the report, we were also careful not to answer all the theories. It's like playing Whack-A-Mole. You're never going to whack them all. . . . The hardcore conspiracy theorists are totally committed. They'd have to repudiate much of their life identity in order not to accept some of that stuff. [They're] not our worry. Our worry is when things become infectious, as happened with the [John F. Kennedy] assassination. Then this stuff can be deeply corrosive to public understanding."

Popular Mechanics decided to step into the void created by the 9/11 Commission and definitively answer the whacky ideas. In March of 2005, the magazine's cover story was "9/11: Debunking the Myths. PM examines the evidence and consults the experts to refute the most persistent conspiracy theories of September 11." The magazine spent 11 pages carefully deconstructing the conspiracies--including theories that the planes that crashed into the World Trade Center couldn't have been passenger jets because they had no windows, puffs of smoke from the towers proved controlled demolitions were used, and that seismographs indicated that the "strongest jolts were all registered at the beginning of the collapse," showing conclusively that explosives must have been used--and explaining why they are incorrect.

The magazine has now expanded that 11 page feature from 18 months ago into a more comprehensive 170 page book. Edited by David Dunbar and Brad Reagan, the book features a foreword by John McCain and contains reports by the National Institute of Standards and Technology on the World Trade Center's collapse and the American Society of Civil Engineers's "Pentagon Building Performance Report." Debunking 9/11 Myths will quickly become the go-to reference for fighting the madness found on the Internet in relation to 9/11. Do you have a friend who emails you the most recent documentary "proving" that a missile impacted the Pentagon or that timed explosions brought down WTC-7? Buy him a copy of this book. He'll thank you later.

Take, for example, the claim that the collapse of the World Trade Center was caused by a controlled demolition. Conspiracy Theorists assert that burning jet fuel is not hot enough to melt steel, so explosions must have been the culprit. As Debunking 9/11 Myths explains, jet fuel burns between 1,100 and 1,200 degrees Celsius, well below the 1,510 degrees necessary to melt steel. But the steel supports of the WTC did not need to melt for the buildings to come down. "Steel begins to lose strength at temperatures as low as 400 degrees Celsius (750 degrees Fahrenheit)," the authors inform us, "and loses roughly 50 percent of its strength at approximately 600 degrees Celsius (1,100 degrees Fahrenheit). At 980 degrees Celsius (1,800 degrees Fahrenheit), it retains less than 10 percent, says Farid Alfawakhiri, the senior engineer of construction codes and standards at the American Iron and Steel Institute." Combined with the fact that the airplanes severed a large number of the load bearing columns in the initial impacts into the twin towers, this weakening of the steel would have done more than enough damage to bring them down. Indeed, engineers are shocked the buildings stood as long as they did.

The book's afterword admits that convincing the "9/11 Truth" community of their waywardness is probably impossible. As James B. Meigs, the editor in chief of Popular Mechanics states, "In a few short weeks, Popular Mechanics had gone from being a 100-year-old journal about science, engineering, car maintenance, and home improvement to being a pivotal player in a global conspiracy on a par with Nazi Germany."

Meigs also laments the "argument by anomaly" fallacy on which conspiracy theorists so often rely: They "generally ignore the mass of evidence that supports the mainstream view and focus strictly on tiny anomalies. . . . If researchers can't 'prove' exactly how the building fell, they say, then there is only one other possible conclusion: Someone blew it up."

As the past five years have shown, simply ignoring the conspiracy theorists will not do the trick; on the internet, in particular, they multiply like mosquitoes. Debunking 9/11 Myths does much to drain the swamp and stop the spread of the crazy theories from propagating through the ether.